Heliopause

node

The outer boundary of the heliosphere: the surface where solar wind plasma gives way to interstellar plasma. It has no wall and no visible edge, so crossing it is detected by what the instruments stop and start seeing — a sharp drop in low-energy particles coming from the Sun, a simultaneous rise in galactic cosmic rays arriving from outside, and a jump in the density of the surrounding electrons. Voyager 1 crossed on 25 August 2012 at 121.6 AU; Voyager 2 crossed on 5 November 2018 at 119 AU. The confirmations came differently. Voyager 1's plasma instrument had failed in 1980, so the density had to be inferred from plasma oscillations recorded by the plasma wave subsystem — an electron oscillation near 2.6 kHz implying about 0.08 electrons per cubic centimetre, some forty times the density of the solar wind at that distance. Voyager 2 measured the plasma directly, and found a boundary layer about 1.5 AU thick before the crossing and a transition that took less than a day. Not a place.

A node is not a place. Drawing it on a map would assert something about the world that no stored fact supports.